1. Field of the Invention
The present invention relates to an information output unit used in a recording apparatus of the type in which recording is carried out while shifting the position of output from a plurality of output parts relative to a recording medium on which information is to be recorded by the output parts. More particularly, the present invention relates to improvements is such an information output unit in order to prevent information from being recorded in overlapping fashion on the recording medium.
2. Description of the Prior Art
In driving output parts of information such as semiconductor laser, LED and thermal head with pulsed outputs, it is generally difficult to obtain a high repetitive frequency. This is because when peak power of the pulsed output is increased while keeping the pulse width constant, thermal energy accumulated therein is also increased unduly. This inconvenience is shown in FIG. 1.
In FIG. 1, T.sub.1 is the pulse width, P.sub.0 is the optical output and T.sub.0 is pulse period. If one wishes to increase the optical output maintaining the pulse width constant without increasing the thermal energy accumulated in the unit, there is required a longer pulse period. This means that the duty (T.sub.1 /T.sub.0) becomes necessarily smaller and the repetitive frequency becomes lower accordingly. The same is also applicable to the case that a longer pulse width is selected as T.sub.1. This will also result in a smaller duty and a lower repetitive frequency.
This inconvenience is caused primarily from the fact that the higher the peak power is or the longer the pulse width is, the larger thermal energy is accumulated in the unit and therefore a longer cooling time is required so as to prevent the elements from being damaged by heat. When the recording medium to be used is of relatively low sensitivity, a picture image must be recorded thereon using a relatively high peak power and long pulse width, which in turn reduces the repetitive frequency. As a result, a long recording time is required to make a picture of one sheet. For facsimile apparatus and the like it is generally said that the running cost is determined by the price of the recording medium and the time required for tranmitting and receiving information. Theefore, it has been desired to provide such recording apparatus which enables out the carrying of recording using a recording medium of relatively low sensitivity (cheap recording medium) without the necessity of long recording time (high speed recording).